The present invention relates to creating an improved coupling structure which provides a strong coupling force and avoids use of welding or other permanent joining manufacturing approach. Embodiments are also directed to designing structures which are designed to destructively disassemble with a different and more desirable fragmentation pattern.
One purpose of various embodiments of the invention is to securely assemble a structure, such as a hollow steel enclosure. An exemplary assembly can be designed to remain secure after strong impacts and repeated abuse. One exemplary assembly can be mechanical and designed avoiding the use of welding, adhesives or threads. Aesthetically, an exemplary assembly can minimize a seam. One exemplary need for certain embodiments of the invention arose from a desire to enclose a pressed explosive within a rugged steel case.
Some methods of assembly include at least welding, threading, adhesive bonding, pressing and shrink fitting. There is a need for a fragmentation structure with improved performance. Some resulting designs can include a solid warhead case surrounding a pressed explosive. One advantage of this design is that it combines energy transfer and economic benefits of breaking a case (rather than projecting embedded objects in a composite case) and an added chemical energy available from pressed explosive relative to cast or chemically cured compositions. Additionally, production and logistical needs of a pressed explosive production process are more efficient and environmentally friendly relative to cast or cured processes.
Existing solutions to forming a body for some fragmentation involve preassembly of the enclosure and then pouring the explosive in through a small opening. Often this involves welding an assembly. Welding can result in altering the metallurgical properties to the extent that fragmentation performance is compromised. Additionally, the geometry of the interface is affected by welding and difficult to control. Welding after explosive loading is unsafe. Other approaches (threading, etc.) of pre-assembly are possible but prevent the application of a pressed explosive as access to the cavity remains limited to a small opening.
Threading the enclosure around an explosive load is undesired due to safety and production concerns. Threads provide the opportunity to initiate stray explosive material with friction generated heat and are generally considered bad practice for energetic production. Another need is a requirement to minimize a distance of threaded interfaces which trends towards the need of fine threads. Additionally, threading gives rise to a need for rotating equipment. Another need is to provide an ability to provide a “final set” in pressed explosives which can be facilitated by a design employing pressing an assembly closed.
A press fit assembly, with and without adhesive bonding, was investigated. Various embodiments showed promise as it met all of the production requirements. However, it was not able to withstand rough handling testing believed required for various applications. Experimental efforts included experimentation with various metal to metal retaining adhesive compounds which did not provide necessary coupling results.
Various designs and methods of manufacturing have been developed including a “snap” fit assembly design. One exemplary design provided sufficient mechanical interface to remain assembled without movement after impacts and rough handling as well as avoiding structural designs which would interfere with fragmentation of assembly material in and next to various mechanical interfaces including various snap fit structures. Additionally, various design embodiments provided a capacity for production with various advantages including a design that required relatively little force to assemble but resulted in a need for a large force to pull apart a mechanical interface. An exemplary mechanical interface in accordance with various embodiments of the invention does not require chemical (adhesive) bonding and can have a strength greater than enclosure sections mechanically coupled. Further, if desired, snap fit assembled parts have the ability to rotate relative to each other.
Apparatuses and methods associated with an enclosure or structure are provided including two sections that are adapted with a snap-fit interlocking structure. Various embodiments of the enclosure or structure are formed with various case hardening or embrittlement processes to increase embrittlement or hardness of the enclosure or structure so as to create a structure or enclosure which has a desired fragmentation capacity while still maintaining sufficient material properties to permit snap-fit insertion of one section into another section and withstand substantial impacts. Embodiments also provide an interlocking structure that minimizes differences in fragmentation or fracturing capacity as contrasted with other portions of the structure or enclosure. An embodiment of the invention includes an enclosure where one section of the enclosure or structure has a first thickness and the second section has a second thickness wherein the first and second thicknesses are different. In some embodiments, one section is thinner than another section.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.